A goal of electronics manufacturers has been to reduce power consumption in electronic devices. Reducing consumption of power lowers the heat generated by the device, thereby increasing the reliability and decreasing the operating cost of the device. In addition, reducing the consumption of power allows battery-powered portable electronic devices, such as cellular telephones, portable music players, laptop computers, and portable gaming devices, to operate for longer periods without recharging or charging the batteries.
Various techniques have been devised for reducing power consumption of electronic devices. These techniques include decreasing the amount of circuitry on a chip so as to reduce the power consumption of the chip. Power management units may also be used to reduce the power consumption. One power reduction technique includes the capability of stopping clock signals that drive circuits which are inactive in the chip for a period of time. A device employing such a technique includes a power management unit (PMU) that detects or predicts inactive circuits and accordingly stops clock signals associated with the inactive circuits. By turning off clock signals that drive inactive circuits, power consumption of the electronic device decreases. Additionally, removing power from inactive circuits may reduce leakage currents within the circuits. Other techniques include reducing the frequency of clock signals that drive circuits during modes of operation that are not time critical and removing power from inactive circuits.
Systems to manage power that use the above mentioned power reduction techniques monitor activities within the electronic device. For example, the PMU may couple directly through control lines to a microprocessor and peripheral devices. The control lines permit the PMU to determine the activities that occur in the microprocessor and peripheral devices. Depending on what activities the PMU detects, the PMU may responsively power down circuits, reduce the clock signal frequencies, or stop selected clock signals.
As described above, power management may reduce power consumption in an electronic device, decrease heat generation, increase reliability, and decrease cost. However, current power management techniques are difficult to design and verify that the techniques are operating properly and may lead to unpredictable and unstable operation of the electronic device. Thus, a power management system and method that is simple to design and verify and ensures reliable and predictable operation of the electronic device would be preferred.